They look like photos of a girls' night out but these are actually drawings - done with BIC ballpoint pens.

The stunning pictures, which can measure three metres high, are drawn by Spanish artist Juan Francisco Casas, based on snapshots of his pals.

Casas, 31, can use up to four of the humble 14p pens to create each drawing - but he always uses blue nibs.

The artist said: "It is very aesthetic on the white paper." The only drawback is that he can't delete any mistakes. Casas, whose work is now on show in Madrid, said: "Wrong at the beginning is better."

Ballpoint pens were invented in 1938 by Hungarian Laszlo Biro. A British firm took over the patent to produce pens for the RAF and the first ones went on sale in the UK during 1946.

The BIC pen, a variation on the original design, went on sale in France in 1950.